1. Field of the Invention
The present invention relates to a spin valve magneto-resistance head and a method of fabricating the same and, more particularly, a spin valve magnetoresistive head for reading information signal from a magnetic recording medium and a method of fabricating the same.
2. Description of the Related Art
As a magnetic transducer for reading information signals from a magnetic recording medium such as a hard disk, magnetic card, or magnetic tape, a magnetoresistive head having high reading sensitivity is well known.
Recently, as a device capable of achieving a higher magnetoresistance effect, a magnetic transducer utilizing a spin valve magnetoresistance effect has been set forth in U.S. Pat. No. 5,206,590.
FIGS. 1A to 1C shows sectional shapes of the magnetic transducer utilizing the spin valve magnetoresistance effect and an operational principle thereof. As shown in FIGS. 1A to 1C, a first soft magnetic layer 102, a nonmagnetic layer 103, a second soft magnetic layer 104 and an antiferromagnetic layer 105 are formed on a substrate 101 in that order. The antiferromagnetic layer 105 is coupled to the second soft magnetic layer 104 by means of exchange coupling to prevent easy change of the direction of magnetization M1 of the second soft magnetic layer 104. For this reason, the second soft magnetic layer 104 is called a pin layer, and the first soft magnetic layer 102 is called a free layer.
The spin valve magnetoresistance effect is defined as a phenomenon wherein electric resistance of respective above layers formed on the substrate 101 are varied by changing a relative angle .theta. between the direction of magnetization M1 of the second soft magnetic layer 104 and the direction of magnetization M2 of the first soft magnetic layer 102. Since the direction of magnetization M2 of the first soft magnetic layer 102 can be changed correspondingly to magnitude of an external magnetic field H, smallest electric resistance of a resultant film can be obtained if the direction of magnetization M2 of the first soft magnetic layer 102 coincides with the direction of magnetization M1 of the second soft magnetic layer 104 (i.e., the intersecting angle .theta. becomes zero), whereas largest electric resistance of the resultant film can be attained if the direction of magnetization M2 is directed opposedly to the direction of magnetization M1 of the second soft magnetic layer 104.
Next, change in electric resistance due to the spinvalve magnetoresistance effect will be explained in detail.
(1) FIG. 1A shows a state wherein the external magnetic field H is not applied, or a state wherein the direction of the external magnetic field H coincides with directions of magnetization M1, M2 of the first soft magnetic layer 102 and the second soft magnetic layer 104.
In this state, the directions of magnetization M1, M2 of the first soft magnetic layer 102 and the second soft magnetic layer 104 formed opposedly to each other via the nonmagnetic layer 103 are directed in the same direction. Therefore, the intersecting angle .theta. of the directions of magnetization M1, M2 becomes zero. At this time, scattering of conduction electrons flowing in the first soft magnetic layer 102 and the second soft magnetic layer 104 and the nonmagnetic layer 103 is decreased. Thus, the electric resistance R of these layers becomes small.
(2) FIG. 1B shows a state wherein the external magnetic field H with the opposite direction to the direction of magnetization M1 of the second soft magnetic layer 104 is applied.
In this state, if the external magnetic field H with a magnitude permitting only the first soft magnetic layer 102 to direct in the opposite direction to that of the magnetization M1 of the second soft magnetic layer 104 is applied, the intersecting angle .theta. between the magnetization M1, M2 becomes 180.degree.. In this case, scattering of conduction electrons in respective layers of the first soft magnetic layer 102 and the second soft magnetic layer 104 and the nonmagnetic layer 103 is increased because the directions of magnetization M1, M2 do not coincide with each other. Thus, the electric resistance R of these layers becomes large.
(3) FIG. 1C shows a state wherein the external magnetic field H with a magnitude permitting the direction of magnetization M1 of the second ferromagnetic layer by removing exchange coupling of the antiferromagnetic layer 105 and the second ferromagnetic layer is applied.
In this state, the directions of magnetization M1, M2 of the first soft magnetic layer 102 and the second soft magnetic layer 104 coincide with each other. Therefore, the intersecting angle .theta. becomes zero so that electric resistance R is decreased.
With the above, in the spin valve magnetoresistive head, the electric resistance R of the first soft magnetic layer 102 and the second soft magnetic layer 104 and the nonmagnetic layer 103 can be changed in response to the direction and magnitude of the external magnetic field H. Therefore, information included in the magnetic field supplied from the magnetic medium may be read by detecting change in the electric resistance R. The electric field caused by the magnetic medium generates external magnetic field H.
In such spin valve magnetoresistive head, in general, as a material of the antiferromagnetic layer 105 used for suppressing change in magnetization M1 of the second soft magnetic layer 104, iron-manganese (FeMn) has been used. But, there is a drawback in that characteristics of the head device deteriorate since the FeMn is readily oxidized.
On the contrary, the spin valve magnetoresistive head without such antiferromagnetic layer has been set forth in Patent Application Publication (KOKAI) 4-247607. In this head device, in order to obtain different coercive force, two soft magnetic layers sandwiching the nonmagnetic layer therebetween are formed respectively of different materials.
However, since the upper crystal structure depends on the lower crystal structure, the crystal structure of the upper soft magnetic layer changes because of difference of crystal structures. For this reason, in contrast to the case wherein two soft magnetic layers are formed of the same materials, magnetic characteristics of the upper soft magnetic layer become different. As a result, this decreases a change ratio of magnetic resistance (resistance change ratio/applied external magnetic field).